Microfeature workpieces and methods for forming interconnects in microfeature workpieces

ABSTRACT

Methods for forming interconnects in microfeature workpieces, and microfeature workpieces having such interconnects are disclosed herein. The microfeature workpieces may have a terminal and a substrate with a first side carrying the terminal and a second side opposite the first side. In one embodiment, a method includes (a) constructing an electrically conductive interconnect extending from the terminal to at least an intermediate depth in the substrate with the interconnect electrically connected to the terminal, and (b) removing material from the second side of the substrate so that a portion of the interconnect projects from the substrate.

TECHNICAL FIELD

The present invention relates to methods for forming interconnects inmicrofeature workpieces and microfeature workpieces formed using suchmethods.

BACKGROUND

Microelectronic devices, micromechanical devices, and other devices withmicrofeatures are typically formed by constructing several layers ofcomponents on a workpiece. In the case of microelectronic devices, aplurality of dies are fabricated on a single workpiece, and each diegenerally includes an integrated circuit and a plurality of bond-padscoupled to the integrated circuit. The dies are separated from eachother and packaged to form individual microelectronic devices that canbe attached to modules or installed in other products.

One aspect of fabricating and packaging such dies is forminginterconnects that electrically couple conductive components located indifferent layers. In some applications, it may be desirable to forminterconnects that extend completely through the dies or through asignificant portion of the dies. Such interconnects electrically couplebond-pads or other conductive elements proximate to one side of the diesto conductive elements proximate to the other side of the dies.Through-wafer interconnects, for example, are constructed by formingdeep vias on the front side and/or backside of the workpiece and inalignment with corresponding bond-pads at the front side of theworkpiece. The vias are often blind vias in that they are closed at oneend. The blind vias are then filled with a conductive fill material.After further processing, the workpiece is thinned to reduce thethickness of the final dies. Solder balls or other external electricalcontacts are subsequently attached to the through-wafer interconnects atthe backside and/or the front side of the workpiece. The solder balls orexternal contacts can be attached either before or after singulating thedies from the workpiece.

Conventional processes for forming external contacts on through-waferinterconnects include (a) depositing a dielectric layer on the backsideof the workpiece, (b) forming a photoresist on the dielectric layer, (c)patterning and developing the photoresist, (d) etching the dielectriclayer to form holes aligned with corresponding interconnects, (e)removing the photoresist from the workpiece, and (f) forming conductiveexternal contacts in the holes in the dielectric layer. One concern withforming external contacts on the backside of a workpiece is thatconventional processes are relatively expensive because patterning thephotoresist requires a mask. Masks are expensive and time-consuming toconstruct because they require very expensive photolithography equipmentto achieve the tolerances required in semiconductor devices.Accordingly, there is a need to reduce the cost of forming externalcontacts on workpieces with through-wafer interconnects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1I illustrate stages of a method for forming interconnects in amicrofeature workpiece in accordance with one embodiment of theinvention.

FIG. 1A is a schematic side cross-sectional view of a portion of theworkpiece at an intermediate stage after partially forming a pluralityof interconnects.

FIG. 1B is a schematic side cross-sectional view of the area 1B shown inFIG. 1A with the workpiece flipped over.

FIG. 1C is a schematic side cross-sectional view of the portion of theworkpiece after thinning the substrate from the second side.

FIG. 1D is a schematic side cross-sectional view of the portion of theworkpiece after selectively removing additional material from the secondside of the substrate so that the interconnect projects from thesubstrate.

FIG. 1E is a schematic side cross-sectional view of the area 1E shown inFIG. 1D after forming a recess in the second end portion of theinterconnect.

FIG. 1F is a schematic side cross-sectional view of the portion of theworkpiece after forming a dielectric structure across the second side ofthe substrate and the second end portion of the interconnect.

FIG. 1G is a schematic side cross-sectional view of the portion of theworkpiece after removing sections of the interconnect and the dielectricstructure.

FIG. 1H is a schematic side cross-sectional view of the portion of theworkpiece after removing the section of the first dielectric layer fromthe recess in the interconnect.

FIG. 1I is a schematic side cross-sectional view of the portion of theworkpiece after forming a conductive member at the second end portion ofthe interconnect.

FIGS. 2A-2C illustrate stages in a method for forming interconnects in amicrofeature workpiece in accordance with another embodiment of theinvention.

FIG. 2A is a schematic side cross-sectional view of a portion of theworkpiece at an intermediate stage after partially forming aninterconnect.

FIG. 2B is a schematic side cross-sectional view of the portion of theworkpiece after removing sections of the interconnect and the dielectricstructure.

FIG. 2C is a schematic side cross-sectional view of the portion of theworkpiece after forming the conductive member on the exposed surface ofthe interconnect.

FIGS. 3A-3C illustrate stages in a method for forming interconnects in amicrofeature workpiece in accordance with another embodiment of theinvention.

FIG. 3A is a schematic side cross-sectional view of a portion of theworkpiece at an intermediate stage after partially forming aninterconnect.

FIG. 3B is a schematic side cross-sectional view of the portion of theworkpiece after removing sections of the interconnect and the dielectricstructure.

FIG. 3C is a schematic side cross-sectional view of the workpiece afterforming a conductive member on the exposed surface of the interconnect.

DETAILED DESCRIPTION A. Overview

The following disclosure describes several embodiments of methods forforming interconnects in microfeature workpieces, and microfeatureworkpieces having such interconnects. One aspect of the invention isdirected to methods of forming an interconnect in a microfeatureworkpiece having a terminal and a substrate with a first side carryingthe terminal and a second side opposite the first side. An embodiment ofone such method includes (a) constructing an electrically conductiveinterconnect extending from the terminal to at least an intermediatedepth in the substrate, and (b) removing material from the second sideof the substrate so that a portion of the interconnect projects from thesubstrate. The material can be removed from the second side of thesubstrate by thinning the substrate so that a surface of theinterconnect is exposed and selectively etching the substrate so thatthe portion of the interconnect projects from the substrate.

In another embodiment, a method includes providing a microfeatureworkpiece having (a) a substrate with a first side and a second sideopposite the first side, (b) a terminal carried by the first side of thesubstrate, and (c) an electrically conductive interconnect extendingfrom the terminal through the substrate and projecting from the secondside of the substrate. The method further includes applying a dielectriclayer to the second side of the substrate and the portion of theinterconnect projecting from the second side of the substrate, andremoving a section of the dielectric layer to expose a surface of theinterconnect with the interconnect intersecting a plane defined by theremaining section of the dielectric layer.

In another embodiment, a method includes forming an electricallyconductive interconnect having a first portion at the terminal and asecond portion at an intermediate depth in the substrate. Theelectrically conductive interconnect is electrically connected to theterminal. The method further includes thinning the substrate from thesecond side to at least the second portion of the interconnect, applyinga dielectric layer to the second side of the substrate and the secondportion of the interconnect, and exposing a surface of the secondportion of the interconnect without photolithography.

Another aspect of the invention is directed to microfeature workpieces.In one embodiment, a microfeature workpiece includes a substrate and amicroelectronic die formed in and/or on the substrate. The substrate hasa first side and a second side opposite the first side. The die includesa terminal at the first side of the substrate and an integrated circuitoperably coupled to the terminal. The workpiece further includes anelectrically conductive interconnect extending from the terminal throughthe substrate such that a portion of the interconnect projects from thesecond side of the substrate. The interconnect is electrically coupledto the terminal.

In another embodiment, a microfeature workpiece includes a substrate anda microelectronic die formed in and/or on the substrate. The substratehas a first side and a second side opposite the first side. The dieincludes a terminal at the first side of the substrate and an integratedcircuit operably coupled to the terminal. The workpiece further includes(a) a hole extending through the terminal and the substrate, (b) adielectric layer on the second side of the substrate defining a plane,and (c) an electrically conductive interconnect. The interconnectincludes a conductive fill material in the hole and a conductive layerin the hole between the conductive fill material and the substrate. Boththe conductive fill material and the conductive layer are electricallycoupled to the terminal and extend from the terminal through thesubstrate. Moreover, both the conductive fill material and theconductive layer project from the substrate such that the conductivefill material and the conductive layer intersect the plane.

Specific details of several embodiments of the invention are describedbelow with reference to interconnects extending from a terminalproximate to the front side of a workpiece, but the methods andinterconnects described below can be used for other types ofinterconnects within microelectronic workpieces. Several detailsdescribing well-known structures or processes often associated withfabricating microelectronic devices are not set forth in the followingdescription for purposes of clarity. Also, several other embodiments ofthe invention can have different configurations, components, orprocedures than those described in this section. A person of ordinaryskill in the art, therefore, will accordingly understand that theinvention may have other embodiments with additional elements, or theinvention may have other embodiments without several of the elementsshown and described below with reference to FIGS. 1A-3C.

The term “microfeature workpiece” is used throughout to includesubstrates upon which and/or in which microelectronic devices,micromechanical devices, data storage elements, optics, and otherfeatures are fabricated. For example, microfeature workpieces can besemiconductor wafers, glass substrates, dielectric substrates, or manyother types of substrates. Many features on such microfeature workpieceshave critical dimensions less than or equal to 1 μm, and in manyapplications the critical dimensions of the smaller features are lessthan 0.25 μm or even less than 0.1 μm. Where the context permits,singular or plural terms may also include the plural or singular term,respectively. Moreover, unless the word “or” is expressly limited tomean only a single item exclusive from other items in reference to alist of at least two items, then the use of “or” in such a list is to beinterpreted as including (a) any single item in the list, (b) all of theitems in the list, or (c) any combination of the items in the list.Additionally, the term “comprising” is used throughout to mean includingat least the recited feature(s) such that any greater number of the samefeatures and/or types of other features and components are notprecluded.

B. Embodiments of Methods for Forming Interconnects in MicrofeatureWorkpieces

FIGS. 1A-1I illustrate stages of a method for forming interconnects in amicrofeature workpiece 100 in accordance with one embodiment of theinvention. FIG. 1A, for example, is a schematic side cross-sectionalview of a portion of the workpiece 100 at an intermediate stage afterpartially forming a plurality of interconnects 140. The workpiece 100can include a substrate 110 and a plurality of microelectronic dies 120formed in and/or on the substrate 110. The substrate 110 has a firstside 112 and a second side 114 opposite the first side 112. Thesubstrate 110 is generally a semiconductor wafer, and the dies 120 arearranged in a die pattern on the wafer. The individual dies 120 includeintegrated circuitry 122 (shown schematically) and a plurality ofterminals 124 (e.g., bond-pads) electrically coupled to the integratedcircuitry 122. The terminals 124 shown in FIG. 1A are external featuresat the first side 112 of the substrate 110. In other embodiments,however, the terminals 124 can be internal features that are embedded atan intermediate depth within the substrate 110. Moreover, in additionalembodiments, the dies 120 can have different features to performdifferent functions. For example, the individual dies may furtherinclude an image sensor (e.g., CMOS image sensor or CCD image sensor)for capturing pictures or other images in the visible spectrum, ordetecting radiation in other spectrums (e.g., IR or UV ranges).

In previous processing steps, a first dielectric layer 130 was appliedto the first side 112 of the substrate 110, and the interconnects 140were partially formed in the workpiece 100. The first dielectric layer130 can be a polyimide material or other suitable nonconductivematerials. For example, the first dielectric layer 130 can be parylene,a low temperature chemical vapor deposition (low temperature CVD)material such as silicon nitride (Si₃N₄), silicon oxide (SiO₂), and/orother suitable materials. The foregoing list of dielectric materials isnot exhaustive. The conductive interconnects 140 extend from the firstdielectric layer 130 to an intermediate depth in the substrate 110. Asdescribed in greater detail below with regard to FIG. 1B, the conductiveinterconnects 140 can include several layers of conductive material thatare electrically coupled to corresponding terminals 124. Suitablemethods for forming the portion of the interconnects 140 illustrated inFIG. 1A are disclosed in U.S. patent application Ser. Nos. 10/713,878;10/867,352; 10/879,398; 11/027,443; 11/056,211; 11/169,546; 11/217,877;and 11/218,243, which are incorporated herein by reference. Afterpartially forming the interconnects 140, the workpiece 100 canoptionally be attached to a support member 190 with an adhesive 192 toprovide rigidity to the workpiece 100 during subsequent processingsteps.

FIG. 1B is a schematic side cross-sectional view of the area 1B shown inFIG. 1A with the workpiece 100 flipped over. The workpiece 100 includesan interconnect hole 180 extending from the terminal 114 to anintermediate depth in the substrate 110, a second dielectric layer 132in the interconnect hole 180, and a vent hole 182 extending from theinterconnect hole 180 to the second side 114 of the substrate 110. Thesecond dielectric layer 132 electrically insulates components in thesubstrate 110 from the interconnect 140. The second dielectric layer 132can be an ALD (atomic layer deposition) aluminum oxide material appliedusing a suitable deposition process or another suitable low temperatureCVD oxide. In another embodiment, the second dielectric layer 132 caninclude a silane-based and/or an aluminum-based oxide material. In stillfurther embodiments, the second dielectric layer 132 can include othersuitable dielectric materials.

The illustrated interconnect 140 is formed in the interconnect hole 180and has a first end portion 142 at the first dielectric layer 130 and asecond end portion 144 at an intermediate depth in the substrate 110.The illustrated interconnect 140 includes a diffusion barrier layer 150deposited over the second dielectric layer 132 in the hole 180, a seedlayer 152 formed over the barrier layer 150 in the hole 180, aconductive layer 154 deposited over the seed layer 152 in the hole 180,and a conductive fill material 152 formed over the conductive layer 154in the hole 180. The diffusion barrier layer 150 can be a layer oftantalum that is deposited onto the workpiece 100 using physical vapordeposition (PVD) and has a thickness of approximately 150 Angstroms. Inother embodiments, the barrier layer 150 may be deposited onto theworkpiece 100 using other vapor deposition processes, such as CVD,and/or may have a different thickness. In either case, the barrier layer150 is not limited to tantalum, but rather may be composed of tungstenor other suitable materials that help contain the conductive fillmaterial 156 in the interconnect hole 180.

The seed layer 152 can be deposited using vapor deposition techniques,such as PVD, CVD, atomic layer deposition, and/or plating. The seedlayer 152 can be composed of Cu or other suitable materials. Thethickness of the seed layer 152 may be about 2000 Angstroms, but couldbe more or less depending on the depth and aspect ratio of the hole 180.The conductive layer 154 can be Cu that is deposited onto the seed layer152 in an electroless plating operation, electroplating operation, oranother suitable method. The thickness of the conductive layer 154 canbe about 1 micron, however, in other embodiments the conductive layer154 can have a different thickness and/or include other suitablematerials. In additional embodiments, the workpiece 100 may include asecond conductive layer (not shown) that is deposited over theconductive layer 154 in the hole 180. The second conductive layer can beNi or other suitable materials that function as a wetting agent forfacilitating deposition of subsequent materials into the hole 180.

The conductive fill material 156 can include Cu, Ni, Co, Ag, Au, SnAgCusolder, AuSn solder, a solder having a different composition, or othersuitable materials or alloys of materials having the desiredconductivity. The conductive fill material 156 may be deposited into thehole 180 using plating processes, solder wave processes, screen printingprocesses, reflow processes, vapor deposition processes, or othersuitable techniques. In other embodiments, the interconnects may have adifferent structure. For example, the interconnects may have additionallayers in lieu of or in addition to the layers described above.

FIG. 1C is a schematic side cross-sectional view of the portion of theworkpiece 100 after thinning the substrate 110 from the second side 114.The substrate 110 can be thinned by grinding, dry etching, chemicaletching, chemical polishing, chemical-mechanical polishing, or othersuitable processes. The thinning process may also remove a section ofthe second end portion 114 of the interconnect 140. For example, in oneembodiment, the initial thickness of the substrate 110 is approximately750 microns and the interconnect 140 extends to an intermediate depth ofapproximately 150 microns in the substrate 110, and the post-thinningthickness T of the substrate 110 is approximately 140 microns. Thesethicknesses can be different in other embodiments. After thinning theworkpiece 100, the illustrated interconnect 140 includes an exposedsurface 146 at the second end portion 144.

FIG. 1D is a schematic side cross-sectional view of the portion of theworkpiece 100 after selectively removing additional material from thesecond side 114 of the substrate 110 so that the interconnect 140projects from the substrate 110. The additional material can be removedvia a plasma etch with SF₆ or another suitable etchant that is selectiveto silicon. Alternatively, the additional material can be removed withother processes. In either case, after thinning the substrate 110, thesecond end portion 144 of the interconnect 140 projects a first distanceD₁ from the second side of the substrate 110. In several embodiments,the first distance D₁ is between approximately 5 and 10 microns,although the first distance D₁ can be less than 5 microns or more than10 microns in other embodiments. The first distance D₁ is selected basedon the subsequent processing and application requirements.

FIG. 1E is a schematic side cross-sectional view of the area 1E shown inFIG. 1D after forming a recess 158 in the second end portion 144 of theinterconnect 140. In the illustrated embodiment, the recess 158 isformed by removing a portion of the conductive fill material 156 fromthe interconnect 140. The conductive fill material 156 can be removed bya wet etch process with an etchant that is selective to the conductivefill material 156 and, consequently, removes the conductive fillmaterial 156 at a faster rate than the seed and/or conductive layers 152and/or 154. The illustrated recess 158 extends from the surface 146 ofthe interconnect 140 to a surface 157 of the conductive fill material156, and has a depth D₂ less than the first distance D₁. The depth D₂ ofthe recess 158 is selected based on the subsequent processing andapplication requirements. In other embodiments, such as the embodimentsdescribed below with reference to FIGS. 2A-3C, the interconnects may notinclude a recess in the second end portion 144.

FIG. 1F is a schematic side cross-sectional view of the portion of theworkpiece 100 after forming a dielectric structure 170 across the secondside 114 of the substrate 110 and the second end portion 144 of theinterconnect 140. The illustrated dielectric structure 170 includes afirst dielectric layer 172 and a second dielectric layer 174 depositedon the first dielectric layer 172. The first dielectric layer 172 can beparylene HT and have a thickness of approximately 0.5 micron. In otherembodiments, other dielectric materials can be used and/or havedifferent thicknesses. The second dielectric layer 174 can be an oxidesuch as silicon oxide (SiO₂) and/or other suitable materials that aredeposited by chemical vapor deposition and/or other suitable processes.In additional embodiments, the dielectric structure 170 can include adifferent number of layers.

FIG. 1G is a schematic side cross-sectional view of the portion of theworkpiece 100 after removing sections of the interconnect 140 and thedielectric structure 170. The sections of the interconnect 140 and thedielectric structure 170 can be removed by grinding, dry etching,chemical etching, chemical polishing, chemical-mechanical polishing, orother suitable processes. In the illustrated embodiment, the workpiece100 is polished to remove portions of the second dielectric layer 132,the barrier layer 150, the seed layer 152, the conductive layer 154, thefirst dielectric layer 172, and the second dielectric layer 174. Thevolume of material removed is selected so that (a) the recess 158 in theinterconnect 140 has a desired depth D₃, and (b) the interconnect 140projects a desired distance D₄ from an exterior surface 175 of thedielectric structure 170. In other embodiments, such as the embodimentdescribed below with reference to FIGS. 3A-3C, the interconnect may notproject from the exterior surface 175 of the dielectric structure 170.In either case, the interconnect 140 intersects a plane defined by thedielectric structure 170.

FIG. 1H is a schematic side cross-sectional view of the portion of theworkpiece 100 after removing the section of the first dielectric layer172 from the recess 158 in the interconnect 140. The section of thefirst dielectric layer 172 can be removed from the recess 158 by aplasma etching process (e.g., O₂ plasma) or another suitable method thatselectively removes the first dielectric layer 172 without significantlyeffecting the dielectric structure 170 formed on the substrate 110.

FIG. 1I is a schematic side cross-sectional view of the portion of theworkpiece 100 after forming a conductive member 160 on the second endportion 144 of the interconnect 140. The illustrated conductive member160 is a cap disposed in the recess 158 and extending over the barrierlayer 150, the seed layer 152, and the conductive layer 154. The capprojects a desired distance D₅ from the substrate 110 and forms anexternal contact for connection to an external device. The conductivemember 160 can be electrolessly plated onto the second end portion 144of the interconnect 140 or formed using other suitable processes. Theconductive member 160 can include Ni or other suitable conductivematerials. In other embodiments, the interconnect 140 may not includethe conductive member 160. For example, the second end portion 144 ofthe interconnects 140 can be attached directly to an external device, ora conductive coupler (e.g., a solder ball) can be attached directly tothe second end portion 144.

One feature of the method illustrated in FIGS. 1A-1I is that theinterconnect 140 projects from the substrate 110. As a result, thesection of the dielectric structure 170 covering the interconnect 140can be removed by a simple polishing process without exposing thebackside of the substrate 110. The resulting exposed surface 146 on theinterconnect 140 may form an external contact to which an externaldevice can be attached. Alternatively, the conductive member 160 can bedisposed on the exposed surface 146 and form the external contact. Ineither case, an advantage of this feature is that the illustrated methoddoes not require expensive and time-consuming photolithography processesto form external contacts on the backside of the workpiece 100.

Another advantage of the method illustrated in FIGS. 1A-1I is that theinterconnect 140 can be sized to project a desired distance from theexternal surface 175 of the dielectric structure 170. The distance canbe selected based on the application requirements for the die 110. Forexample, in applications in which the die 110 is stacked on another die,the distance may be selected to provide a desired gap between the twodies.

C. Additional Embodiments of Methods for Forming Interconnects inMicrofeature Workpieces

FIGS. 2A-2C illustrate stages in a method for forming interconnects in amicrofeature workpiece 200 in accordance with another embodiment of theinvention. FIG. 2A, for example, is a schematic side cross-sectionalview of a portion of the workpiece 200 at an intermediate stage afterpartially forming an interconnect 240. The illustrated workpiece 200 isgenerally similar to the workpiece 100 described above with reference toFIGS. 1A-1F. For example, the illustrated workpiece 200 includes asubstrate 110, an interconnect 240 extending through and projecting fromthe substrate 110, and a dielectric structure 270 formed over thesubstrate 110 and the interconnect 240. The illustrated interconnect240, however, does not include a recess at the second end portion 244.

FIG. 2B is a schematic side cross-sectional view of the portion of theworkpiece 200 after removing sections of the interconnect 240 and thedielectric structure 270. The sections of the interconnect 240 and thedielectric structure 170 can be removed by grinding, dry etching,chemical etching, chemical polishing, chemical-mechanical polishing, orother suitable processes. The volume of the material removed is selectedso that the interconnect 240 projects a desired distance D₆ from anexterior surface 275 of the dielectric structure 270. The illustratedinterconnect 240 includes a generally planar exposed surface 246extending across the barrier layer 150, the seed layer 152, theconductive layer 154, and the conductive fill material 156.

FIG. 2C is a schematic side cross-sectional view of the portion of theworkpiece 200 after forming a conductive member 260 on the generallyplanar exposed surface 246 of the interconnect 240. The conductivemember 260 forms part of the electrically conductive interconnect 240and, accordingly, is electrically coupled to the terminal 114 (FIG. 1B).

FIGS. 3A-3C illustrate stages in a method for forming interconnects in amicrofeature workpiece 300 in accordance with another embodiment of theinvention. FIG. 3A, for example, is a schematic side cross-sectionalview of a portion of the workpiece 300 at an intermediate stage afterpartially forming an interconnect 340. The illustrated workpiece 300 isgenerally similar to the workpiece 200 described above with reference toFIG. 2A. For example, the illustrated workpiece 300 includes a substrate110, an interconnect 340 extending through and projecting from thesubstrate 110, and a dielectric structure 370 formed over the substrate110 and the interconnect 340.

FIG. 3B is a schematic side cross-sectional view of the portion of theworkpiece 300 after removing sections of the interconnect 340 and thedielectric structure 370. The sections of the interconnect 340 and thedielectric structure 370 are removed to form a generally planar surfaceacross the workpiece 300 such that an exposed surface 346 of theinterconnect 340 is generally coplanar with an exterior surface 375 ofthe dielectric structure 370.

FIG. 3C is a schematic side cross-sectional view of the workpiece 300after forming a conductive member 360 on the exposed surface 346 of theinterconnect 340. The conductive member 360 forms part of theelectrically conductive interconnect 340 and, accordingly, iselectrically coupled to the terminal 114 (FIG. 1B).

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. For example, many of the elements ofone embodiment can be combined with other embodiments in addition to orin lieu of the elements of the other embodiments. Accordingly, theinvention is not limited except as by the appended claims.

We claim:
 1. A method for forming an interconnect in a microfeature workpiece, the microfeature workpiece including a terminal and a substrate with a first side carrying the terminal and a second side opposite the first side, the method comprising: constructing an electrically conductive interconnect with a barrier material insulating the interconnect from the substrate and covering an end of the interconnect, the interconnect extending from the terminal to at least an intermediate depth in the substrate with the interconnect electrically connected to the terminal; removing material from the second side of the substrate and from the barrier material so that a portion of the interconnect projects from the substrate and the interconnect has an exposed, conductive surface at the end of the interconnect; depositing a first dielectric layer composed of a first material onto the exposed, conductive surface of the portion of the interconnect that projects from the substrate and thereby covering the portion of the interconnect that projects from the substrate; and depositing a second dielectric layer composed of a second material onto the first dielectric layer such that the second dielectric layer covers the first dielectric layer, wherein the first material is different than the second material, and wherein the first material is removable by a removal process that generally does not affect the second dielectric layer.
 2. The method of claim 1 wherein: constructing the electrically conductive interconnect comprises forming an interconnect having a conductive fill material in a hole in the substrate and a conductive layer in the hole between the conductive fill material and the substrate, with the conductive fill material and the conductive layer extending from the terminal to the at least intermediate depth in the substrate; removing material from the second side of the substrate comprises (a) thinning the substrate from the second side so that a section of the interconnect is exposed, and (b) selectively etching the substrate so that the portion of the interconnect projects from the substrate; and the method further comprises (a) removing a section of the conductive fill material from the portion of the interconnect so that the conductive fill material is recessed relative to the conductive layer, (b) applying a dielectric layer to the second side of the substrate and the portion of the interconnect after removing the section of the conductive fill material, (c) removing at least a section of the dielectric layer covering the portion of the interconnect to expose a section of the interconnect, and (d) forming a conductive member on the section of the interconnect.
 3. The method of claim 1 wherein removing material from the second side of the substrate comprises: thinning the substrate from the second side so that a section of the interconnect is exposed; and selectively etching the substrate so that the portion of the interconnect projects from the substrate.
 4. The method of claim 1 wherein: constructing the electrically conductive interconnect comprises forming an interconnect having a conductive fill material in a hole in the substrate and a conductive layer in the hole between the conductive fill material and the substrate, with the conductive fill material and the conductive layer extending from the terminal to the at least intermediate depth in the substrate; and the method further comprises removing a section of the conductive fill material from the portion of the interconnect so that the conductive fill material is recessed relative to the conductive layer.
 5. The method of claim 1 wherein the first material comprises parylene HT and the second material comprises silicon oxide (SiO₂).
 6. The method of claim 1 wherein depositing at least one of the first and second dielectric layers comprises depositing by chemical vapor deposition.
 7. The method of claim 1, further comprising forming a conductive member on the portion of the conductive interconnect.
 8. The method of claim 1, further comprising plating a conductive cap onto the portion of the conductive interconnect.
 9. The method of claim 3 wherein selectively etching comprises etching the substrate so that the portion of the interconnect projects between approximately 5 and 10 microns from the substrate.
 10. The method of claim 3 wherein thinning the substrate comprises at least one of grinding, chemical-mechanical polishing, mechanical polishing, or chemical polishing the substrate.
 11. The method of claim 1 wherein removing material from the second side of the substrate occurs after constructing the electrically conductive interconnect.
 12. A method for forming an interconnect in a microfeature workpiece, the method comprising: providing a microfeature workpiece having (a) a substrate with a first side and a second side opposite the first side, (b) a terminal carried by the first side of the substrate, and (c) an electrically conductive interconnect extending from the terminal through the substrate and projecting from the second side of the substrate; applying a first dielectric layer composed of a first material to the second side of the substrate and to an uncoated, conductive surface of the portion of the interconnect projecting from the second side of the substrate; applying a second dielectric layer composed of a second material to the first dielectric layer such that the second dielectric layer covers, wherein the first material and the second material are different materials, and wherein the first material is removable by a first process and the second material is removable by a second process; removing a section of the first and second dielectric layers to expose a surface of the interconnect with the interconnect intersecting a plane defined by the remaining section of the dielectric layers.
 13. The method of claim 12 wherein providing the microfeature workpiece comprises: constructing the electrically conductive interconnect in the substrate with the interconnect extending from the terminal to at least an intermediate depth in the substrate; and removing material from the second side of the substrate so that the portion of the interconnect projects from the substrate.
 14. The method of claim 12 wherein at least one of applying the first dielectric layer and applying the second dielectric layer comprises depositing parylene.
 15. The method of claim 12 wherein at least one of the first and second processes polishing the workpiece.
 16. The method of claim 12, further comprising forming a conductive member on the exposed surface of the interconnect.
 17. The method of claim 12 wherein at least one of the first and second processes comprises removing the section of the respective dielectric layer without photolithography.
 18. The method of claim 12 wherein removing the section of the first and second dielectric layers comprises: removing a portion of the section of the second dielectric layer in a first process; and removing a portion of the remaining dielectric layer in a second process different than the first process.
 19. A method for forming an interconnect in a microfeature workpiece, the microfeature workpiece including a terminal and a substrate with a first side carrying the terminal and a second side opposite the first side, the method comprising: forming an electrically conductive interconnect having a first portion at the terminal and a second portion at an intermediate depth in the substrate, the electrically conductive interconnect being electrically connected to the terminal; thinning the substrate from the second side to at least the second portion of the interconnect; applying a first dielectric layer composed of a first material to the second side of the substrate and thereby covering the second portion of the interconnect after thinning the substrate; applying a second dielectric layer composed of a second material to at least a portion of the first dielectric layer such that the second dielectric layer covers at least a portion of the first dielectric layer that covers the second portion of the interconnect, wherein the first and second materials are different materials, and wherein the first material is susceptible to etching and the second material is resistant to etching.
 20. The method of claim 19 wherein thinning the substrate comprises removing material from the second side of the substrate so that the second portion of the interconnect projects from the substrate.
 21. The method of claim 19, further comprising selectively etching the substrate so that the second portion of the interconnect projects from the substrate.
 22. The method of claim 19 wherein: forming the electrically conductive interconnect comprises constructing an interconnect having a conductive fill material in a hole in the substrate and a conductive layer in the hole between the conductive fill material and the substrate, with the conductive fill material and the conductive layer extending from the terminal to the at least intermediate depth in the substrate; and the method further comprises removing a section of the conductive fill material from the portion of the interconnect so that the conductive fill material is recessed relative to the conductive layer.
 23. The method of claim 19, further comprising forming a conductive member on the exposed surface of the conductive interconnect.
 24. The method of claim 19 wherein removing a portion of the second dielectric layer comprises at least one of grinding, chemical-mechanical polishing, mechanical polishing, or chemical polishing.
 25. The method of claim 1 wherein depositing the first dielectric layer comprises depositing through a first process, and depositing the second dielectric layer comprises depositing through a second process different from the first process.
 26. The method of claim 12 wherein applying the first dielectric layer comprises applying through a first process, and applying the second dielectric layer to the first dielectric layer comprises applying through a second process, wherein the first process is different from the second process.
 27. The method of claim 19 wherein applying the dielectric layer to the second side of the substrate comprises applying through a first process, and applying the second dielectric layer to at least a portion of the first dielectric layer comprises applying through a second process, wherein the first process is different from the second process, and at least one of the first and second processes comprises chemical vapor deposition.
 28. A method for constructing an interconnect in a microfeature workpiece with an initial dielectric layer attached to a first side of a substrate, the method comprising: forming an interconnect extending through the initial dielectric layer and extending to at least an intermediate depth in the substrate; thinning the substrate by removing material from a second side of the substrate and from the interconnect; removing additional material from the second side of the substrate using a selective etchant such that a portion of the interconnect protrudes from the second side of the substrate; forming a recess in the portion of the interconnect by removing a portion of material from the portion of the interconnect; forming a dielectric structure over the portion of the interconnect, the dielectric structure comprising a first dielectric layer and a second dielectric layer on the first dielectric layer, wherein the first and second dielectric layers are composed of different materials; removing sections of the dielectric structure and the portion of the interconnect such that the second dielectric layer is removed to expose the first dielectric layer; and removing the first dielectric layer from the portion of the interconnect to form a recess in the portion of the interconnect to expose conductive fill material in the interconnect.
 29. The method of claim 28 wherein forming the interconnect comprises insulating the interconnect from the substrate with dielectric material.
 30. The method of claim 28 wherein forming the interconnect comprises forming a conductive fill material separated from the substrate by dielectric material, a diffusion barrier, a seed layer, and a conductive layer.
 31. The method of claim 28 wherein forming the dielectric structure comprises using at least one of atomic layer deposition, physical vapor deposition, and chemical vapor deposition.
 32. The method of claim 28 wherein forming the interconnect comprises forming a conductive fill material using at least one of plating processes, solder wave processes, screen printing processes, reflow processes, and vapor deposition processes.
 33. The method of claim 28 wherein removing sections of the dielectric structure comprises using an etchant that is selective to at least one of the first and the second dielectric layers.
 34. The method of claim 28 wherein thinning the substrate by removing material comprises removing material by at least one of grinding, dry etching, chemical etching, chemical polishing, and chemical-mechanical polishing.
 35. The method of claim 28 wherein removing additional material comprises removing the additional material using a plasma etching process.
 36. The method of claim 1, further comprising exposing a portion of the first dielectric layer through the second dielectric layer over the portion of the interconnect.
 37. The method of claim 1, further comprising removing the exposed portion of the first dielectric layer through the selective removal process.
 38. The method of claim 19, further comprising removing a portion of the second dielectric layer covering the portion of the first dielectric layer.
 39. The method of claim 19, further comprising exposing a surface of the second portion of the interconnect using an etching process that does not substantially affect the second dielectric layer. 